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Issue #13575: there is only one class type.

This commit is contained in:
Florent Xicluna 2011-12-12 18:54:29 +01:00
parent 9d57481f04
commit aa6c1d240f
8 changed files with 25 additions and 81 deletions
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12
Doc/howto/descriptor.rst
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@ -36,9 +36,7 @@ continuing through the base classes of ``type(a)`` excluding metaclasses. If the
looked-up value is an object defining one of the descriptor methods, then Python
may override the default behavior and invoke the descriptor method instead.
Where this occurs in the precedence chain depends on which descriptor methods
were defined. Note that descriptors are only invoked for new style objects or
classes (a class is new style if it inherits from :class:`object` or
:class:`type`).
were defined.
Descriptors are a powerful, general purpose protocol. They are the mechanism
behind properties, methods, static methods, class methods, and :func:`super()`.
@ -89,8 +87,6 @@ of ``obj``. If ``d`` defines the method :meth:`__get__`, then ``d.__get__(obj)`
is invoked according to the precedence rules listed below.
The details of invocation depend on whether ``obj`` is an object or a class.
Either way, descriptors only work for new style objects and classes. A class is
new style if it is a subclass of :class:`object`.
For objects, the machinery is in :meth:`object.__getattribute__` which
transforms ``b.x`` into ``type(b).__dict__['x'].__get__(b, type(b))``. The
@ -115,7 +111,6 @@ The important points to remember are:
* descriptors are invoked by the :meth:`__getattribute__` method
* overriding :meth:`__getattribute__` prevents automatic descriptor calls
* :meth:`__getattribute__` is only available with new style classes and objects
* :meth:`object.__getattribute__` and :meth:`type.__getattribute__` make
different calls to :meth:`__get__`.
* data descriptors always override instance dictionaries.
@ -128,10 +123,7 @@ and then returns ``A.__dict__['m'].__get__(obj, A)``. If not a descriptor,
``m`` is returned unchanged. If not in the dictionary, ``m`` reverts to a
search using :meth:`object.__getattribute__`.
Note, in Python 2.2, ``super(B, obj).m()`` would only invoke :meth:`__get__` if
``m`` was a data descriptor. In Python 2.3, non-data descriptors also get
invoked unless an old-style class is involved. The implementation details are
in :c:func:`super_getattro()` in
The implementation details are in :c:func:`super_getattro()` in
`Objects/typeobject.c <http://svn.python.org/view/python/trunk/Objects/typeobject.c?view=markup>`_
and a pure Python equivalent can be found in `Guido's Tutorial`_.

2
Lib/pickle.py
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@ -375,7 +375,7 @@ class _Pickler:
# allowing protocol 0 and 1 to work normally. For this to
# work, the function returned by __reduce__ should be
# called __newobj__, and its first argument should be a
# new-style class. The implementation for __newobj__
# class. The implementation for __newobj__
# should be as follows, although pickle has no way to
# verify this:
#

2
Lib/pickletools.py
View File

@ -1639,6 +1639,8 @@ opcodes = [
is pushed on the stack.
NOTE: checks for __safe_for_unpickling__ went away in Python 2.3.
NOTE: the distinction between old-style and new-style classes does
not make sense in Python 3.
"""),
I(name='OBJ',

6
Modules/gc_weakref.txt
View File

@ -15,8 +15,8 @@ have been called before resurrection). At best (and this has been an
historically common bug), tp_clear empties an instance's __dict__, and
"impossible" AttributeErrors result. At worst, tp_clear leaves behind an
insane object at the C level, and segfaults result (historically, most
often by setting a new-style class's mro pointer to NULL, after which
attribute lookups performed by the class can segfault).
often by setting a class's mro pointer to NULL, after which attribute
lookups performed by the class can segfault).
OTOH, it's OK to run Python-level code that can't access unreachable
objects, and sometimes that's necessary. The chief example is the callback
@ -119,7 +119,7 @@ isn't easy to stumble into by accident while Python is running, and, indeed,
it took quite a while to dream up failing test cases. Zope3 saw segfaults
during shutdown, during the second call of gc in Py_Finalize, after most
modules had been torn down. That creates many trash cycles (esp. those
involving new-style classes), making the problem much more likely. Once you
involving classes), making the problem much more likely. Once you
know what's required to provoke the problem, though, it's easy to create
tests that segfault before shutdown.

31
Objects/typeobject.c
View File

@ -100,15 +100,13 @@ PyType_Modified(PyTypeObject *type)
static void
type_mro_modified(PyTypeObject *type, PyObject *bases) {
/*
Check that all base classes or elements of the mro of type are
Check that all base classes or elements of the MRO of type are
able to be cached. This function is called after the base
classes or mro of the type are altered.
Unset HAVE_VERSION_TAG and VALID_VERSION_TAG if the type
inherits from an old-style class, either directly or if it
appears in the MRO of a new-style class. No support either for
custom MROs that include types that are not officially super
types.
has a custom MRO that includes a type which is not officially
super type.
Called from mro_internal, which will subsequently be called on
each subclass when their mro is recursively updated.
@ -124,11 +122,7 @@ type_mro_modified(PyTypeObject *type, PyObject *bases) {
PyObject *b = PyTuple_GET_ITEM(bases, i);
PyTypeObject *cls;
if (!PyType_Check(b) ) {
clear = 1;
break;
}
assert(PyType_Check(b));
cls = (PyTypeObject *)b;
if (!PyType_HasFeature(cls, Py_TPFLAGS_HAVE_VERSION_TAG) ||
@ -488,7 +482,7 @@ type_set_bases(PyTypeObject *type, PyObject *value, void *context)
if (!PyType_Check(ob)) {
PyErr_Format(
PyExc_TypeError,
"%s.__bases__ must be tuple of old- or new-style classes, not '%s'",
"%s.__bases__ must be tuple of classes, not '%s'",
type->tp_name, Py_TYPE(ob)->tp_name);
return -1;
}
@ -1619,7 +1613,7 @@ mro_internal(PyTypeObject *type)
type->tp_mro = tuple;
type_mro_modified(type, type->tp_mro);
/* corner case: the old-style super class might have been hidden
/* corner case: the super class might have been hidden
from the custom MRO */
type_mro_modified(type, type->tp_bases);
@ -1676,9 +1670,8 @@ best_base(PyObject *bases)
return NULL;
}
}
if (base == NULL)
PyErr_SetString(PyExc_TypeError,
"a new-style class can't have only classic bases");
assert (base != NULL);
return base;
}
@ -3196,7 +3189,7 @@ object_set_class(PyObject *self, PyObject *value, void *closure)
}
if (!PyType_Check(value)) {
PyErr_Format(PyExc_TypeError,
"__class__ must be set to new-style class, not '%s' object",
"__class__ must be set to a class, not '%s' object",
Py_TYPE(value)->tp_name);
return -1;
}
@ -3811,8 +3804,8 @@ inherit_special(PyTypeObject *type, PyTypeObject *base)
that the extension type's own factory function ensures).
Heap types, of course, are under our control, so they do
inherit tp_new; static extension types that specify some
other built-in type as the default are considered
new-style-aware so they also inherit object.__new__. */
other built-in type as the default also
inherit object.__new__. */
if (base != &PyBaseObject_Type ||
(type->tp_flags & Py_TPFLAGS_HEAPTYPE)) {
if (type->tp_new == NULL)
@ -6352,7 +6345,7 @@ supercheck(PyTypeObject *type, PyObject *obj)
{
/* Check that a super() call makes sense. Return a type object.
obj can be a new-style class, or an instance of one:
obj can be a class, or an instance of one:
- If it is a class, it must be a subclass of 'type'. This case is
used for class methods; the return value is obj.

2
Python/errors.c
View File

@ -665,7 +665,7 @@ PyErr_NewException(const char *name, PyObject *base, PyObject *dict)
if (bases == NULL)
goto failure;
}
/* Create a real new-style class. */
/* Create a real class. */
result = PyObject_CallFunction((PyObject *)&PyType_Type, "sOO",
dot+1, bases, dict);
failure:

7
Python/pythonrun.c
View File

@ -474,7 +474,7 @@ Py_Finalize(void)
flush_std_files();
/* Collect final garbage. This disposes of cycles created by
* new-style class definitions, for example.
* class definitions, for example.
* XXX This is disabled because it caused too many problems. If
* XXX a __del__ or weakref callback triggers here, Python code has
* XXX a hard time running, because even the sys module has been
@ -1348,11 +1348,6 @@ parse_syntax_error(PyObject *err, PyObject **message, const char **filename,
_Py_IDENTIFIER(offset);
_Py_IDENTIFIER(text);
/* old style errors */
if (PyTuple_Check(err))
return PyArg_ParseTuple(err, "O(ziiz)", message, filename,
lineno, offset, text);
/* new style errors. `err' is an instance */
if (! (v = _PyObject_GetAttrId(err, &PyId_msg)))

44
Tools/gdb/libpython.py
View File

@ -402,7 +402,7 @@ class ProxyAlreadyVisited(object):
def _write_instance_repr(out, visited, name, pyop_attrdict, address):
'''Shared code for use by old-style and new-style classes:
'''Shared code for use by all classes:
write a representation to file-like object "out"'''
out.write('<')
out.write(name)
@ -481,7 +481,7 @@ class HeapTypeObjectPtr(PyObjectPtr):
def proxyval(self, visited):
'''
Support for new-style classes.
Support for classes.
Currently we just locate the dictionary using a transliteration to
python of _PyObject_GetDictPtr, ignoring descriptors
@ -498,7 +498,7 @@ class HeapTypeObjectPtr(PyObjectPtr):
attr_dict = {}
tp_name = self.safe_tp_name()
# New-style class:
# Class:
return InstanceProxy(tp_name, attr_dict, long(self._gdbval))
def write_repr(self, out, visited):
@ -670,44 +670,6 @@ class PyDictObjectPtr(PyObjectPtr):
pyop_value.write_repr(out, visited)
out.write('}')
class PyInstanceObjectPtr(PyObjectPtr):
_typename = 'PyInstanceObject'
def proxyval(self, visited):
# Guard against infinite loops:
if self.as_address() in visited:
return ProxyAlreadyVisited('<...>')
visited.add(self.as_address())
# Get name of class:
in_class = self.pyop_field('in_class')
cl_name = in_class.pyop_field('cl_name').proxyval(visited)
# Get dictionary of instance attributes:
in_dict = self.pyop_field('in_dict').proxyval(visited)
# Old-style class:
return InstanceProxy(cl_name, in_dict, long(self._gdbval))
def write_repr(self, out, visited):
# Guard against infinite loops:
if self.as_address() in visited:
out.write('<...>')
return
visited.add(self.as_address())
# Old-style class:
# Get name of class:
in_class = self.pyop_field('in_class')
cl_name = in_class.pyop_field('cl_name').proxyval(visited)
# Get dictionary of instance attributes:
pyop_in_dict = self.pyop_field('in_dict')
_write_instance_repr(out, visited,
cl_name, pyop_in_dict, self.as_address())
class PyListObjectPtr(PyObjectPtr):
_typename = 'PyListObject'